1. Field of the Invention
The present invention relates to a forward-reverse rotation device. More specifically, the present invention relates to a forward-reverse rotation device used in a continuously variable transmission.
2. Background Information
Conventional forward-reverse rotation devices generally used in continuously variable transmissions have a planetary gear set having a double planetary gear, a reverse brake, and a forward clutch. In this type of forward-reverse rotation device, the sun gear is coupled to the power input from the engine and the planet carrier is coupled to the output because the gear ratio for reverse is approximately equal to the gear ratio for direct forward drive (i.e., 1:1). During forward motion, the sun gear, which serves as the input, and the planet carrier, which serves as the output, are coupled together directly by the forward clutch.
For example, in one conventional forward-reverse rotation device the sun gear is splined to an external circumferential surface and is near the tip of the input shaft. Further, the clutch drum is also fixed by welding to the external circumferential surface and is near the tip of the input shaft. The planet carrier is coupled to the output shaft via an output hub. The output hub is splined to the output shaft and also welded to the planet carrier.
In another conventional forward-reverse rotation device, the sun gear is formed integrally with the input shaft. The forward clutch drum is coupled to the input shaft via an input hub. The input hub is splined to the input shaft and is also welded to the forward clutch drum. The planet carrier is coupled to the output shaft via an output hub. The output hub is splined to the output shaft and also welded to the to the planet carrier.
In either of these forward-reverse rotation devices, both splines and welding are used to couple the input and output shafts to other members. Welding is generally more difficult than machining to execute and, consequently, is more expensive. There is also the disadvantage of elongating the device in the axial direction.
The output part of the planet carrier is a cylindrical portion that protrudes from the carrier main body toward the output side in the axial direction and has splines formed on its internal circumferential surface. Since the portion of the planet carrier that is supported by the output shaft is displaced or overhangs axially from the center of gravity of the planet carrier, it is easy for the planet carrier have center run out. There is also the possibility that the meshing contact of the double planetary gear will degrade.
In view of the above, there exists a need for a forward-reverse rotation device for a continuously variable transmission that overcomes the above-mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to reduce the manufacturing cost of a forward-reverse rotation device for a continuously variable transmission.
Another object of the present invention is to improve the meshing contact of the double planetary gears in a forward-reverse rotation device for a continuously variable transmission.
The forward-reverse rotation device for a continuously variable transmission in accordance with a first aspect of the present invention has an input shaft, an output shaft, a planetary gear set, a reverse brake, and a forward clutch. The planetary gear set has a sun gear provided on the input shaft, a ring gear, a double planetary gear, and a planet carrier. The planet carrier axially supports the double planetary gear and serves to output power to the output shaft. The reverse brake facilitates and prohibits rotation of the ring gear. The forward clutch couples and releases the input shaft to and from the carrier. The sun gear and some spline teeth are formed integrally on the external circumferential surface of the input shaft. The forward clutch has a clutch drum that has internal splines. The internal splines are press-formed integrally and interlock with the spline teeth.
In this device, the sun gear and spline teeth are formed integrally on the input shaft and the clutch drum interlocks directly with the spline teeth of the input shaft. Thus, unlike the prior art, there is no need for welding and manufacturing costs are reduced.
A forward-reverse rotation device for a continuously variable transmission in accordance with a second aspect of the present invention is the device of the first aspect, wherein a hollow part that is open at the tip is formed in the tip of the input shaft. Further, the tip of the output shaft is positioned inside the hollow part. The planet carrier has a carrier member that has an output part that splines together with the external circumferential surface of the tip of the output shaft inside the hollow part.
With this device, the orientation of the double planetary gear is stable. Further, poor meshing contact is reduced because the output part of the carrier member is disposed inside the hollow part formed in the tip face of the input shaft.
A forward-reverse rotation device for a continuously variable transmission in accordance with a third aspect of the present invention is the device of the second aspect, wherein the sun gear is formed on the external circumferential surface of the input shaft near the tip thereof. Further, the output part of the carrier member is positioned radially inward with respect to the sun gear.
In this device, the orientation of the double planetary gear is stable. Poor meshing contact is also reduced because the output part of the carrier member is positioned radially inward with respect to the sun gear.
A forward-reverse rotation device for a continuously variable transmission in accordance with a fourth aspect of the present invention is the device of the third aspect, wherein the carrier member has a main body part and an output part that is cylindrical. The output part is formed integrally with the main body part to bend therefrom. The output part is disposed inside the hollow part.
In this device, the output part of the carrier member is formed integrally so as to bend from the main body part. Consequently, the manufacturing cost is reduced.
A forward-reverse rotation device for a continuously variable transmission according to a fifth aspect of the present invention is the device of any of the aforementioned aspects, wherein a first toothed part and a second toothed part are formed on the external circumferential surface of the input shaft near the tip thereof. The first toothed part constitutes the sun gear. The second toothed part constitutes the spline teeth. The second toothed part is formed by cutting the height of a toothed part that connects in an uninterrupted manner with and has the same shape as the first toothed part.
This device is easier to fabricate because the second toothed part is formed by cutting a portion of the first toothed part.
A forward-reverse rotation device for a continuously variable transmission in accordance with a sixth aspect of the present invention is the device of any of the aforementioned aspects, wherein the sun gear has an axially facing end face that faces in a direction opposite the tip. Further, the tip face of the clutch drum touches the axially facing end face of the sun gear such that movement of the clutch drum toward the tip is limited.
The structure of this device is simplified because axial movement of the clutch drum is limited by the sun gear.
A forward-reverse rotation device for a continuously variable transmission in accordance with a seventh aspect of the present invention is the device of sixth aspect, wherein an axially opposite end face that faces a direction opposite the tip is formed on the clutch drum. Furthermore, a washer is provided which serves to position the clutch drum with respect to the input shaft in the axial direction by touching the axially opposite end face.
A forward-reverse rotation device for a continuously variable transmission in accordance with an eighth aspect of the present invention is the device of the seventh aspect, wherein a thrust bearing is further provided for supporting the input shaft in the axial direction. The washer is a portion of the thrust bearing.
A forward-reverse rotation device for a continuously variable transmission in accordance with a ninth aspect of the present invention is the device of any one of the first to fourth aspects, wherein an annular groove is formed in the internal splines of the clutch drum. Further, an annular groove is formed at a corresponding position in the splined shaft of the input shaft. The forward-reverse rotation device is also provided with ring member that is inserted into the grooves and to limit axial motion between the clutch drum and the input shaft.
A forward-reverse rotation device for a continuously variable transmission in accordance with a tenth aspect of the present invention is the device of any one of sixth to ninth aspects, wherein the clutch drum has a clutch piston, a return spring, and a holding member. The return spring returns the clutch spring. The holding member holds the return spring. The tip face of the holding member touches the axially facing end face of the sun gear.
A forward-reverse rotation device for a continuously variable transmission in accordance with an eleventh aspect of the present invention has an input shaft, a planetary gear set, a reverse brake, and a forward clutch. The planetary gear set has a sun gear, a ring gear, a double planetary gear, and a planet carrier. The sun gear is provided on the input shaft. The planet carrier supports the double planetary gear. The reverse brake facilitates and prohibits rotation of the ring gear. The forward clutch couples and releases the input shaft to and from the planet carrier. The planet carrier has a carrier member that has an output part positioned at the center of gravity of the planet carrier.
With this device, the orientation of the double planetary gear is stable. Further, poor meshing contact is reduced because the output part of the planet carrier is positioned at the center of gravity of the planet carrier.
A forward-reverse rotation device for a continuously variable transmission in accordance with a twelfth aspect of the present invention is the device of the eleventh aspect, wherein the output part of the carrier member is disposed radially inward with respect to the double planetary gear.
A forward-reverse rotation device for a continuously variable transmission in accordance with a thirteenth aspect of the present invention is the device of the twelfth aspect, wherein a hollow part that opens at the tip is formed in the tip of the input shaft. Further, the output part of the carrier member is disposed inside the hollow part.
A forward-reverse rotation device for a continuously variable transmission in accordance with a fourteenth aspect of the present invention is the device of the thirteenth aspect, wherein the sun gear is formed on the external circumferential surface of the input shaft near the tip thereof. Further, the output part of the carrier member is positioned radially inward with respect to the sun gear.
A forward-reverse rotation device for a continuously variable transmission in accordance with a fifteenth aspect of the present invention is the device of the fourteenth aspect, wherein the carrier member has a main body part. Further, the output part is cylindrical and formed integrally with the main body part to bend therefrom. The output part disposed inside the hollow part. Spline slots are formed on the internal circumferential surface of the output part.